A multi-window system in which plural windows can be displayed is known. In such a multi-window system, in a case where each window corresponds to an application program, and plural windows are displayed, plural application programs are running in parallel. To determine an arrangement of windows in a multi-window system, techniques described in patent documents 1 and 2 are known. The techniques are for arranging windows according to a predetermined algorithm depending on an area of a window, or a number of windows to be displayed, to improve visibility and operability.
In a small information-processing device such as a mobile phone, memory capacity is limited. Therefore, in a case where such an information-processing device implements a multi-window system, a number of application programs that can be executed in parallel is limited. Recently, such information-processing devices have become increasingly sophisticated, and the level of services required by a user or value of services to a user becomes higher. However, a storage area of a memory that is required by an application program for providing such a service has to be increased accordingly. Thus, it is likely that a situation occurs that only a single application program can be executed. However, user demand for parallel execution of plural application programs is high.